1. Field of the Invention
The present invention relates to structures for fixing intake manifolds to engines.
2. Description of the Related Art
A known fixing structure for an intake manifold that distributes intake air to cylinders of a multi-cylinder engine is disclosed in Japanese Laid-Open Patent Publication No. 2003-201928. This fixing structure includes a first mounting device for fixing an end portion on an air inlet side of the intake manifold to the engine, and a second mounting device for fixing an air outlet side of the intake manifold to the engine. With each of the first and second mounting devices, an angle between an installation surface provided on the engine and a mount surface provided on the intake manifold for joining to the installation surface is set to be zero in a free state (non-fixed state) of the intake manifold. Therefore, no bending moment is applied to the intake manifold when the intake manifold is fixed to the engine.
However, in the case of the known fixing structure, there has been a problem known as “waving phenomenon” that generates local vibrations at a portion or portions (such as intake pipes) having rigidity lower than that of the other portion of the intake manifold fixed to the engine. In particular, if the intake pipes are made of resin, large amplitude of local vibrations may be generated.
Therefore, there is a need in the art for preventing or reducing local vibrations of an intake manifold mounted to an engine.